These small, circular, concentric machining marks are called **breech face markings** (or **breech face impressions**). They are individual characteristics imparted to the primer cup or cartridge case head during the firing process. When the firing pin strikes the primer and the propellant ignites, the explosive expansion of gases drives the bullet down the barrel. Simultaneously, an equal and opposite reaction forces the cartridge case rearward with great velocity, slamming the base of the case against the **breech face** of the firearm—the flat, metal surface of the bolt or firing mechanism that supports the cartridge head. The microscopic imperfections, machining marks, and patterns on the breech face (which are unique to that firearm due to manufacturing and wear) are stamped onto the softer metal of the cartridge case head. These markings are often circular or semi-circular striations and are a critical source of evidence for firearms examiners. Using a comparison microscope, they can match breech face markings on a cartridge case found at a crime scene to a test-fired cartridge from a suspect weapon, potentially linking the weapon to the scene.

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Zambia

• Joseph Soko – 101 pts

• Visual Pathway Lesions
• Positive and Negative Symptoms
• Hallucinations and Delusions
• Antipsychotic Medications
• Emergency: Environmental Emergencies